1. Field of the Invention
The present invention relates generally to a fluid-filled vibration-damping device of overall generally cylindrical shape, which is capable of exhibiting vibration-damping effect with respect to vibrations applied thereto primarily in an axial direction thereof on the basis of flows of a non-compressible fluid filled therein. More specifically, the present invention is concerned with such a fluid filled cylindrical vibration-damping device that is novel in construction and applicable to a variety of mounts for automotive vehicles including an engine mount, a body mount, a member mount, a carburetor mount and a strut-bar cushion, for example.
2. Description of the Related Art
A cylindrical vibration-damping device, which includes mutually connected inner shaft member and outer sleeve member via a rubber elastic body, is widely known as one type of a vibration-damping coupling or mount adapted to be installed between two members of a vibration systems so as to elastically connect or support the two members in a vibration-damping fashion. Further, JP-B-7-88866 or JP-A-8-152041 discloses a known example of a fluid-filled cylindrical vibration-damping device that is capable of exhibiting vibration-damping effect with respect to vibrations applied thereto primarily in its axial direction with the help of flows of a non-compressible fluid sealed therein. In the known fluid-filled cylindrical vibration-damping device disclosed in these publication documents, the inner shaft member and the outer sleeve member are elastically connected together at one axial end portions thereof via the elastic body, at the other axial end portions thereof via an flexible layer, and at axially intermediate portions thereof via a rubber partition. Accordingly, the fluid-filled cylindrical vibration-damping device includes a pressure-receiving chamber partially defined by the elastic body and an equilibrium chamber partially defined by the flexible layer, which are formed on axially opposite sides of the rubber partition. These pressure-receiving and equilibrium chambers are both filled with a non-compressible fluid, and are mutually held in fluid communication via an orifice passage.
When the known fluid-filled cylindrical vibration-damping device is subjected to vibrations applied thereto in its axial direction, a relative fluid pressure variation is induced between the pressure-receiving chamber and the equilibrium chamber, causing flows of the fluid through the orifice passages due to fluid pressure differences between the pressure-receiving chamber and the equilibrium chamber.
Meanwhile, the known fluid-filled cylindrical vibration-damping device as disclosed in the above described documents, has suffered from difficulty in obtaining a sufficient amount of fluid flows between the pressure-receiving chamber and the equilibrium chamber through the orifice passage, when subjected to vibration application in its axial direction. As a result, the known fluid-filled cylindrical vibration-damping device is still insufficient in exhibiting vibration-damping effect on the basis of flows of the fluid.
To cope with such a drawback, it has been proposed, as disclosed in JP-A-8-170686, JP-A-9-229128 and JP-A-10-132016, for example, not to be bonded one of the inner and outer peripehral portions of the rubber partition to the inner shaft member or the outer sleeve member so that the peripheral portion of the rubber partition become axially slidable. However, such a non-bonded peripheral portion of the rubber partition with respect to the inner shaft member or the outer sleeve member may cause insufficient fluid tight sealing and durability at the peripheral portion of the rubber portion. This may possibly create a short passage or undesirable fluid communication between the pressure-receiving chamber and the equilibrium chamber through the interface between the non-bonded peripheral portion of the rubber partition and the inner shaft member or the outer sleeve member, resulting in deterioration in vibration-damping effect of the device.
Besides, JP-U-6-22642 has proposed to give a butt like shape to the rubber partition so that the rubber partition extends in an axial direction of the device with a cylindrical shape having an axially intermediate portion that largely expands radially outwardly with an arc shape. However, the proposed rubber partition of butt like shape is simply bent and extended to undergo extension and compression deformation in the axial direction, when being subjected to an axial vibrational load. Therefore, the fluid-filled cylindrical vibration-damping device disclosed in JP-U-6-22642 still suffers from difficulty in generating a sufficient amount of relative pressure variation between the pressure-receiving chamber and the equilibrium chamber. In addition, the rubber partition largely expands into the pressure-receiving chamber, making it difficult for the pressure-receiving chamber to have a sufficient amount of volume. This causes deterioration in vibration-damping capability of the device, especially for vibrations having a relatively large amplitude or stroke.